JP2024044572A - Polypropylene resin composition and method for producing the same - Google Patents

Abstract

[Problem] To provide a polypropylene-based resin composition and a method for producing the same, which can give molded articles having an excellent balance of rigidity, impact resistance, and surface impact resistance. [Solution] A polypropylene-based resin composition containing a polypropylene-based resin (A) including a continuous phase made of a propylene polymer (a1) and a rubber phase made of a copolymer (a2) of ethylene and an α-olefin having 3 to 10 carbon atoms, the content of the copolymer (a2) being 30 to 36 mass% based on the total mass of the polypropylene-based resin (A), the content of ethylene-derived units in the copolymer (a2) being 20 to 40 mass% based on the total mass of the copolymer (a2), the intrinsic viscosity of the xylene-soluble portion of the polypropylene-based resin (A) in tetrahydronaphthalene at 135°C being 0.7 to 2.1 dL/g, and the MFR of the polypropylene-based resin composition at a temperature of 230°C and a load of 2.16 kg being 20 to 36 g/10 min. [Selected Figures] None

Description

The present invention relates to a polypropylene resin composition and a method for producing the same.

Polypropylene is used for various purposes because it has excellent physical properties such as impact resistance, rigidity, transparency, chemical resistance, and heat resistance. Molded articles made of resin compositions containing polypropylene as a main component are sometimes required to have an excellent balance between impact resistance and rigidity. For example, Patent Document 1 discloses a resin composition that allows injection molded products with excellent appearance as well as various mechanical properties to be obtained by adjusting the content of xylene insoluble matter (XI), Mw/Mn, etc. has been done.

JP2019-189818A

The present invention provides a polypropylene resin composition and a method for producing the same, which yield molded articles with an excellent balance of rigidity, impact resistance, and surface impact resistance.

The present invention has the following aspects.
[1] Polypropylene containing a polypropylene resin (A) comprising a continuous phase consisting of a propylene polymer (a1) and a rubber phase consisting of a copolymer (a2) of ethylene and an α-olefin having 3 to 10 carbon atoms. A system resin composition,
The content of the polypropylene resin (A) is 90% by mass or more and 100% by mass or less based on the total mass of the polypropylene resin composition,
The content of the propylene polymer (a1) is 64 to 70% by mass based on the total mass of the polypropylene resin (A),
The content of the copolymer (a2) is 30 to 36% by mass based on the total mass of the polypropylene resin (A),
The content of ethylene-derived units in the copolymer (a2) is 20 to 40% by mass with respect to the total mass of the copolymer (a2),
The xylene-soluble portion of the polypropylene resin (A) has an intrinsic viscosity of 0.7 to 2.1 dL/g in tetrahydronaphthalene at 135°C,
The polypropylene resin composition has an MFR of 20 to 36 g/10 minutes at a temperature of 230° C. and a load of 2.16 kg.
[2] The polypropylene resin composition according to [1], wherein the propylene polymer (a1) has an MFR of 30 to 150 g/10 minutes at a temperature of 230° C. and a load of 2.16 kg.
[3] The polypropylene resin composition according to [1] or [2], wherein the propylene polymer (a1) has an intrinsic viscosity of 0.89 to 1.26 dL/g in tetralin at 135°C.
[4] {[Intrinsic viscosity of the xylene-soluble portion of the polypropylene resin (A) in tetrahydronaphthalene at 135°C]/[Intrinsic viscosity of the propylene polymer (a1) in tetralin at 135°C] The polypropylene resin composition according to any one of [1] to [3], wherein the ratio represented by } is 0.4 to 2.3.
[5] The propylene polymer (a1) and the copolymer (a2) are mixed by polymerization, and the polypropylene resin (A) is prepared using a catalyst containing the following components (a) to (c). The polypropylene resin composition according to any one of [1] to [4], which is a polymerization mixture produced by.
(a) A solid catalyst containing magnesium, titanium, halogen, and a phthalate compound as an electron donor compound (b) An organoaluminum compound (c) An organosilicon compound that is an external electron donor compound [6] [5] The method for producing the polypropylene resin composition described above, in which ethylene monomer and carbon number A method for producing a polypropylene resin composition, comprising the step of polymerizing 3 to 10 α-olefin monomers to obtain the polypropylene resin (A).
(a) Solid catalyst containing magnesium, titanium, halogen, and a phthalate compound as an electron donor compound as essential components (b) Organoaluminum compound (c) Organosilicon compound as an external electron donor compound

By using the polypropylene resin composition of the present invention, it is possible to obtain a molded article having an excellent balance of rigidity, impact resistance and surface impact resistance.
The polypropylene resin composition of the present invention has an excellent balance of the above-mentioned physical properties and is therefore suitable for applications such as food packaging, miscellaneous goods, daily necessities, home appliance parts, electric and electronic parts, automobile parts, housing members, toy members, furniture members, building materials, packaging members, industrial materials, logistics materials, and agricultural materials.

<Polypropylene Resin Composition>
The polypropylene-based resin composition of the present invention contains a polypropylene-based resin (A) (hereinafter also referred to as component (A)) which includes a continuous phase made of a propylene polymer (hereinafter also referred to as component (a1)) and a rubber phase made of a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms (hereinafter also referred to as component (a2)).

The polypropylene resin composition of this embodiment contains an optional ethylene/α-olefin copolymer (B) (hereinafter also referred to as component (B)) which is a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms. It may further include.
The polypropylene resin composition of this embodiment may further include a nucleating agent (C) (hereinafter also referred to as component (C)).
These components (B) and (C) are optional components, and may or may not be included in the polypropylene resin composition of this embodiment.

The content of the polypropylene resin (A) is 90% by mass or more and 100% by mass or less based on the total mass of the polypropylene resin composition, with the lower limit being preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more, and the upper limit being preferably less than 100% by mass.
When the content is equal to or greater than the lower limit of the above range, the above-mentioned effects of the present invention can be sufficiently obtained.
If it is less than the upper limit of the above range, there is room for containing optional components such as component (B) and component (C).

The content of the ethylene/α-olefin copolymer (B) is, for example, preferably 0 to 10 mass%, more preferably 0 to 5 mass%, and even more preferably 0 mass%, relative to the total mass of the components (A) and (B).
When component (B) is contained, the impact resistance and surface impact resistance of the molded article are improved.
When the content is equal to or less than the upper limit of the above range, the rigidity of the molded article is increased, whereas when the content exceeds 10% by mass, the rigidity is decreased, and handling may become difficult.

The content of the nucleating agent (C) is, for example, preferably 0.02 to 0.5 parts by mass, more preferably 0.05 to 0.1 parts by mass, based on 100 parts by mass of the total mass of component (A).
When it is at least the lower limit of the above range, the rigidity of the molded product increases.
If the upper limit of the above range is exceeded, the effect of improving the rigidity of the molded product reaches a ceiling, which is uneconomical.

The polypropylene resin composition has an MFR of 20 to 36 g/10 min at a temperature of 230° C. and a load of 2.16 kg, with the lower limit being preferably 24 g/10 min or more. The upper limit is preferably 34 g/10 min or less, and more preferably 31 g/10 min or less. The MFR is a value measured by the measurement method described below.
If the content is equal to or greater than the lower limit of the above range, insufficient filling of the molding die during injection molding is unlikely to occur.
When the content is equal to or less than the upper limit of the above range, the impact resistance and surface impact resistance of the molded product can be sufficiently improved.

[Polypropylene resin (A)]
The polypropylene-based resin (A) contained in the polypropylene-based resin composition of the present invention is one embodiment of an impact-resistant polypropylene polymer defined in JIS K6921-1, and is composed of two or more phases including a continuous phase of a propylene polymer (component (a1)) and a rubber phase of an ethylene-α-olefin copolymer (component (a2)) present as a dispersed phase in the continuous phase.
The polypropylene resin (A) may be a mixed resin obtained by mixing the components (a1) and (a2) during polymerization, or may be a mixed resin obtained by mixing the components (a1) and (a2) obtained separately by melt kneading. A resin having an excellent balance of rigidity, impact resistance, and surface impact resistance (hereinafter also referred to as "mechanical property balance") can be obtained at a lower cost, and therefore a resin obtained by mixing the components (a1) and (a2) during polymerization (polymerization mixture) is preferred.
In the polymerization mixture, the components (a1) and (a2) can be mixed together on the submicron order, and therefore a polypropylene resin composition based on the polymerization mixture exhibits an excellent balance of mechanical properties.
On the other hand, if a similar homogeneous mixture is realized by simply melt-kneading the separately obtained components (a1) and (a2) to obtain an excellent balance of mechanical properties, the production cost will be high due to the need to go through separate steps such as storage, keeping, transportation, weighing, mixing, melt-kneading, etc., which is also undesirable from the viewpoint of energy costs.
The reason why the polymerization mixture and the mechanical mixture may show different physical properties is presumably due to the difference in the dispersion state of component (a2) in component (a1), but at present, there is no known practical means for analyzing the dispersion state at the molecular level, including the interface state between component (a2) and component (a1). The production method of polypropylene-based resin (A) will be described in detail later.

The ethylene-derived unit content (hereinafter also referred to as "C2") in the propylene polymer (component (a1)) constituting the polypropylene-based resin (A) is 1.0 mass% or less, preferably 0.5 mass% or less, based on the total mass of the propylene polymer.
When C2 is equal to or less than the upper limit, the rigidity of the molded article is increased.
The lower limit of C2 is not particularly limited, and may be 0 mass %.
Therefore, the propylene polymer may be a propylene homopolymer consisting only of propylene-derived units, or a copolymer consisting of 99.0 mass% or more and less than 100 mass% propylene-derived units and more than 0 mass% and 1.0 mass% or less ethylene-derived units. From the viewpoint of increasing the rigidity of the obtained molded article, however, it is preferable that C2 is 0 mass%.
C2 is measured by ¹³ C-NMR spectroscopy.

The content of the propylene polymer (component (a1)) relative to the total mass of the polypropylene resin (A) is 64 to 70 mass%, with the lower limit being preferably 65 mass% or more and more preferably 66 mass% or more, and the upper limit being preferably 69 mass% or less and more preferably 68 mass% or less.
When it is equal to or less than the upper limit of the above range, the impact resistance and surface impact resistance of the molded article are improved.
When the content is equal to or greater than the lower limit of the above range, the risk of blockage of flow paths in production equipment due to deterioration of powder fluidity during production of the polypropylene-based resin (A) can be reduced, so that the polypropylene-based resin (A) can be stably and continuously produced.

The MFR of the propylene polymer (component (a1)) constituting the polypropylene-based resin (A) at a temperature of 230° C. and a load of 2.16 kg is preferably 30 to 150 g/10 min. The lower limit is more preferably 45 g/10 min or more, and the upper limit is more preferably 99 g/10 min or less, and even more preferably 90 g/10 min or less. Here, the MFR is a value measured by the measurement method described later.
If the content is equal to or higher than the lower limit of the above range, insufficient filling into the mold during injection molding is unlikely to occur, whereas if the content is equal to or lower than the upper limit of the above range, the impact resistance and surface impact resistance of the molded product are improved.

The ethylene/α-olefin copolymer (component (a2)) constituting the polypropylene resin (A) is a copolymer having an ethylene-derived unit and an α-olefin-derived unit having 3 to 10 carbon atoms.
The content of ethylene-derived units in component (a2) is 20 to 40% by mass based on the total mass of component (a2), and the lower limit is preferably 25% by mass or more. Further, the upper limit is preferably 38% by mass or less, more preferably 35% by mass or less.
When it is at least the lower limit of the above range, the impact resistance of the molded article at low temperatures increases.
When it is below the upper limit of the above range, the impact resistance of the molded article at room temperature increases.
The content of ethylene-derived units in component (a2) is measured by ¹³ C-NMR method.

The content of the ethylene/α-olefin copolymer (component (a2)) with respect to the total mass of the polypropylene resin (A) is 30 to 36% by mass, and the lower limit is preferably 31% by mass or more, and 32% by mass. The above is more preferable. Further, the upper limit is preferably 35% by mass or less, more preferably 34% by mass or less.
If it is at least the lower limit of the above range, the impact resistance and surface impact resistance of the molded article will increase.
If it is below the upper limit of the above range, it is possible to reduce the risk of clogging the flow path on the production equipment due to deterioration of powder fluidity during the production of polypropylene resin (A), so polypropylene resin (A) can be stably produced. Can be produced continuously.

Examples of the α-olefin constituting the ethylene/α-olefin copolymer (component (a2)) include propylene (1-propene), 1-butene, 1-pentene, 1-hexene, and 1-octene.
Specific examples of the component (a2) include ethylene-propylene copolymers, ethylene-butene copolymers, ethylene-pentene copolymers, ethylene-hexene copolymers, and ethylene-octene copolymers.
Among these, in consideration of improving the productivity of the polypropylene-based resin (A), an ethylene-propylene copolymer is preferred.

<Intrinsic viscosity (IV)>
The intrinsic viscosity of the propylene polymer (component (a1)) at 135° C. in tetralin is preferably 0.89 to 1.26 dL/g. Moreover, 1.00 is more preferable as a lower limit value, and 1.16 is more preferable as an upper limit value.
When it is at least the lower limit of the above range, the advantage of improving the impact resistance and surface impact resistance of the molded article can be obtained. When it is below the upper limit of the above range, the advantage of improved injection moldability can be obtained.
The intrinsic viscosity of the propylene polymer (component (a1)) can be measured in a solvent such as tetralin at 135° C. using a capillary viscometer.

<Intrinsic Viscosity (XSIV)>
The intrinsic viscosity (hereinafter, also referred to as "XSIV") of the xylene soluble matter of the polypropylene resin (A) (component (a1) + component (a2)) is 0.7 to 2.1 dL/g, with the lower limit being preferably 1.4 dL/g or more, more preferably 1.5 dL/g or more, and the upper limit being preferably 2.0 dL/g or less, more preferably 1.9 dL/g or less.
If it is equal to or more than the lower limit of the above range, the impact resistance of the molded article is increased, whereas if it is less than 0.7 dl/g, it becomes difficult to produce the polypropylene-based resin composition.
When the XSIV is equal to or less than the upper limit of the above range, the surface impact resistance of the molded article is improved. It is believed that when the XSIV is high, coarse particles are likely to exist, and cracks are likely to occur from these particles, resulting in poor surface impact resistance, but the present invention is not limited to this hypothesis.
Here, XSIV is a value measured in tetrahydronaphthalene at 135° C. The xylene solubles are a component obtained by dissolving a sample of the polypropylene resin (A) in o-xylene at 135° C., cooling it to 25° C., filtering the cooled solution using filter paper, and evaporating the filtrate to dryness.

<Viscosity ratio>
The ratio represented by {[Intrinsic viscosity (XSIV) of the xylene soluble portion of polypropylene resin (A) (component (a1)+component (a2)) in tetrahydronaphthalene at 135°C]/[Intrinsic viscosity (IV) of propylene polymer (component (a1)) in tetralin at 135°C]} is preferably 0.4 to 2.3. The lower limit is more preferably 1.1 or more, and even more preferably 1.3 or more. The upper limit is more preferably 2.1 or less, and even more preferably 1.9 or less.
When it is equal to or more than the lower limit of the above range, an advantage of high impact resistance is obtained.
When it is equal to or less than the upper limit of the above range, advantages of excellent surface impact resistance and small shrinkage rate can be obtained.

[Ethylene-α-olefin copolymer (B)]
The ethylene/α-olefin copolymer (B) is a copolymer of ethylene and an α-olefin having a carbon number of 4 to 10. Examples of the α-olefin include 1-butene, 1-pentene, 1-hexene, and 1-octene.
Specific examples of the ethylene/α-olefin copolymer (B) include ethylene/butene copolymers, ethylene/pentene copolymers, ethylene/hexene copolymers, and ethylene/octene copolymers.
Among these, in consideration of the ease of procurement as a raw material, economic efficiency, and the like, ethylene-butene copolymers and ethylene-octene copolymers are preferred.

The ethylene/α-olefin copolymer (B) preferably has an MFR of 1 to 40 g/10 min at a temperature of 190° C. and a load of 2.16 kg, where the MFR is a value measured in accordance with JIS K6921-2.
When the content is equal to or more than the lower limit of the above range, the flowability of the polypropylene resin composition is increased, and when the content is equal to or less than the upper limit of the above range, the impact resistance of the molded product is increased.

[Nucleating Agent (C)]
The nucleating agent (C) is also called a crystal nucleating agent. As the nucleating agent (C), a known nucleating agent that is contained in a conventional polypropylene resin composition can be used, and a nucleating agent selected from a nonitol-based nucleating agent, a sorbitol-based nucleating agent, a phosphate-based nucleating agent, a triaminobenzene derivative nucleating agent, a carboxylate metal salt nucleating agent, and a xylitol-based nucleating agent is preferred. Talc can also be used as a nucleating agent. From the viewpoint of reducing the odor of the injection molded article, a phosphate-based nucleating agent is preferred.
Examples of nucleating agents having a nonitol-based structure include 1,2,3-trideoxy-4,6:5,7-bis-[(4-propylphenyl)methylene]-nonitol, examples of nucleating agents having a xylitol-based structure include bis-1,3:2,4-(5',6',7',8'-tetrahydro-2-naphthaldehyde benzylidene) 1-allyl xylitol, bis-1,3:2,4-(3',4'-dimethylbenzylidene) 1-propyl xylitol, and examples of nucleating agents having a sorbitol-based structure include bis-1,3:2,4-(4'-ethylbenzylidene) 1-allyl sorbitol, bis-1,3:2,4-(3'-methyl-4'-fluoro-benzylidene) 1-propyl sorbitol, bis-1,3:2,4-(3',4'-dimethyl benzylidene) 1-propyl sorbitol. 2,4-(4'-ethylbenzylidene)-1-allyl sorbitol, mono 2,4-(3'-bromo-4'-ethylbenzylidene)-1-allyl sorbitol, bis-1,3:2,4-(4'-ethylbenzylidene)-1-allyl sorbitol, bis-1,3:2,4-(3',4'-dimethylbenzylidene)-1-methyl sorbitol, bis(p-methylbenzylidene)sorbitol, 1,3:2,4-bis-o-(4-methylbenzylidene)-D-sorbitol, and the like.
Examples of commercially available nonitol-based crystal nucleating agents include Millad NX8000 (manufactured by Milliken Japan Co., Ltd.), and examples of commercially available sorbitol-based crystal nucleating agents include RiKAFAST R-1 (manufactured by New Japan Chemical Co., Ltd.), Millad 3988 (manufactured by New Japan Chemical Co., Ltd.), Gelall E-200 (manufactured by New Japan Chemical Co., Ltd.), and Gelall MD (manufactured by New Japan Chemical Co., Ltd.).
Examples of phosphate ester-based crystal nucleating agents include sodium 2,2-methylenebis(4,6-di-tert-butylphenyl)phosphate, aluminum 2,2'-methylenebis(4,6-di-tert-butylphenyl)phosphate, lithium 2,2'-methylenebis(4,6-di-tert-butylphenyl)phosphate, etc. Examples of commercially available phosphate ester-based crystal nucleating agents include Adeka STAB NA-11 (manufactured by ADEKA CORPORATION), Adeka STAB NA-21 (manufactured by ADEKA CORPORATION), Adeka STAB NA-71 (manufactured by ADEKA CORPORATION), etc.
Examples of triaminobenzene derivative crystal nucleating agents include 1,3,5-tris(2,2-dimethylpropanamide)benzene, etc. Examples of commercially available triaminobenzene derivative crystal nucleating agents include IRGACLEAR XT386 (manufactured by BASF Japan Ltd.) and RIKACLEAR PC1 (manufactured by New Japan Chemical Co., Ltd.).
Examples of the metal carboxylate nucleating agent include calcium 1,2-cyclohexanedicarboxylate, etc. Examples of commercially available metal carboxylate nucleating agents include Hyperform HPN-20E (manufactured by Milliken Japan Co., Ltd.).
These crystal nucleating agents may be used alone or in combination of two or more kinds.

[Other ingredients]
The polypropylene resin composition of the present invention may contain additives other than the polypropylene resin (A), the ethylene/α-olefin copolymer (B), and the nucleating agent (C) as optional components within a range that does not impair the effects of the present invention. Agents may also be included.
The additives include, for example, antioxidants, neutralizing agents, nucleating agents other than the above-mentioned nucleating agents, weathering agents, pigments (organic or inorganic), internal and external lubricants, anti-blocking agents, antistatic agents, and chlorine absorbers. agent, heat stabilizer, light stabilizer, ultraviolet absorber, slip agent, antifog agent, flame retardant, dispersant, copper damage inhibitor, plasticizer, foaming agent, antifoaming agent, crosslinking agent, peroxide, oil Exhibitions, etc. These additives may be used alone or in combination of two or more. The content may be a known amount.

<Method of producing polypropylene resin composition>
As a method for producing the polypropylene-based resin composition of the present invention, a method of mixing the polypropylene-based resin (A) and, if necessary, the optional ethylene-α-olefin copolymer (B) and the optional nucleating agent (C) and then melt-kneading the mixture can be mentioned.
The mixing method may be a dry blending method using a mixer such as a Henschel mixer, a tumbler, or a ribbon mixer.
The melt-kneading method includes a method of mixing while melting using a mixer such as a single screw extruder, a twin screw extruder, a Banbury mixer, a kneader, a roll mill, etc. The melting temperature in the case of melt-kneading is preferably 160 to 350° C., more preferably 170 to 260° C. After melt-kneading, the mixture may be further pelletized.

[Method for producing polypropylene resin (A)]
The polypropylene resin (A) may be obtained by mixing a propylene polymer (component (a1)) and an ethylene/α-olefin copolymer (component (a2)) during polymerization, or may be obtained by separately produced components. It may also be obtained by mixing (a1) and component (a2) by melt-kneading.
It is preferable that the polypropylene resin (A) is a polymerization mixture in which component (a1) and component (a2) are mixed during polymerization.
Such a polymerization mixture is obtained by polymerizing ethylene monomer and α-olefin monomer in the presence of component (a1). According to this method, not only productivity increases, but also the dispersibility of component (a2) in component (a1) increases, so the balance of mechanical properties of the molded product obtained using this method improves.

The following describes the case where propylene monomer is used as the α-olefin monomer, but the same method can be used when other α-olefin monomers are used.

As a method for producing the polymerization mixture, a multi-stage polymerization method is typically used. For example, in a first-stage polymerization reactor of a polymerization apparatus equipped with two-stage polymerization reactors, a propylene monomer and, if necessary, an ethylene monomer are polymerized to obtain a propylene polymer, and the obtained propylene polymer is supplied to a second-stage polymerization reactor, and the ethylene monomer and the propylene monomer are polymerized in the second-stage polymerization reactor to obtain the polymerization mixture.
The polymerization conditions may be the same as known polymerization conditions. For example, the first-stage polymerization conditions include a slurry polymerization method in which propylene is in a liquid phase and has high monomer density and productivity. The second-stage polymerization conditions include a gas phase polymerization method, which generally makes it easy to produce a copolymer that is highly soluble in propylene.
The polymerization temperature is preferably 50 to 90° C., more preferably 60 to 90° C., and even more preferably 70 to 90° C. When the polymerization temperature is equal to or higher than the lower limit of the above range, the productivity and the stereoregularity of the obtained polypropylene are superior.
The polymerization pressure is preferably 25 to 60 bar (2.5 to 6.0 MPa), more preferably 33 to 45 bar (3.3 to 4.5 MPa) when carried out in a liquid phase, and is preferably 5 to 30 bar (0.5 to 3.0 MPa), more preferably 8 to 30 bar (0.8 to 3.0 MPa) when carried out in a gas phase.
Polymerization (polymerization of propylene monomer, polymerization of ethylene monomer and propylene monomer, etc.) is usually carried out using a catalyst. During polymerization, hydrogen may be added, if necessary, to adjust the molecular weight. By adjusting the molecular weight of the propylene polymer or ethylene-propylene copolymer, the MFR of the polypropylene resin (A) and therefore the MFR of the polypropylene resin composition can be adjusted.
Before the polymerization in the first-stage polymerization reactor, propylene may be prepolymerized in order to form polymer chains on the solid catalyst component, which serve as a foothold for the subsequent main polymerization. The prepolymerization is usually carried out at 40° C. or less, preferably 30° C. or less, more preferably 20° C. or less.

As the catalyst, a known olefin polymerization catalyst can be used.
As a catalyst for polymerizing an ethylene monomer and a propylene monomer in the presence of the propylene polymer, a stereospecific Ziegler-Natta catalyst is preferable, and a catalyst containing the following components (A), (B), and (C) (hereinafter also referred to as "catalyst (X)") is particularly preferable.
(a) A solid catalyst containing, as essential components, magnesium, titanium, a halogen, and a phthalate compound as an electron donor compound.
(a) Organoaluminum compounds.
(c) Organosilicon compounds that are external electron donor compounds.

The polypropylene-based resin (A) is preferably produced by a process including a step of polymerizing an ethylene monomer and an α-olefin monomer (e.g., a propylene monomer) in the presence of the propylene polymer using a catalyst (X) to obtain the polypropylene-based resin. By using the catalyst (X), a polypropylene-based resin (A) having each physical property within the above-mentioned range can be easily obtained.
The molecular weight and stereoregularity distribution of the propylene polymer obtained varies depending on the catalyst used (especially the electron donor compound of component (A)), and the difference affects the crystallization behavior, but the details of the relationship have not been clarified. In order to clarify this, it is necessary to analyze the molecular weight distribution and stereoregularity distribution together as a molecular structure, but it is complicated because components with different molecular weights and stereoregularities affect each other in the crystallization process, making it more difficult to interpret the effect of stereoregularity distribution on crystallization behavior. Furthermore, since actual injection molding is performed at a very high speed and in a fluid state, it is not easy to grasp the phenomenon even if advanced analytical techniques are used. Therefore, it is almost impossible to specify the difference in crystallization behavior due to the stereoregularity distribution in terms of numerical values, etc., in polypropylene resin compositions obtained using a specific catalyst. The molecular weight distribution and stereoregularity distribution change due to thermal deterioration during melt kneading, peroxide treatment, etc., in addition to the above-mentioned types of catalyst.

Component (a) is prepared using, for example, a titanium compound, a magnesium compound, and an electron donor compound.
As the titanium compound used for component (A), a tetravalent titanium compound represented by the general formula: Ti(OR) _g X _4-g (R is a hydrocarbon group, X is a halogen, 0≦g≦4) is used. suitable. Examples of the hydrocarbon group include methyl, ethyl, propyl, butyl, etc., and examples of the halogen include Cl, Br, etc.
More specific titanium compounds include titanium tetrahalides such as TiCl ₄ , TiBr ₄ , TiI ₄ ; Ti(OCH ₃ )Cl ₃ , Ti(OC ₂ H ₅ )Cl ₃ , Ti(O _n -C _{4 Trihalogenated} alkoxytitaniums such as _H9 ) _Cl3 , Ti( _{OC2H5 ) Br3} , Ti(O- _isoC4H9 ) _Br3 ; Ti( _OCH3 ) _{2Cl2 ,} Ti( _{OC2H 5} ) _{Dihalogenated alkoxytitaniums such as 2Cl2 , Ti} ( _{On - C4H9 ) 2Cl2 ,} Ti( _OC2H5 ) _2Br2 ; Ti( _OCH3 ) _3Cl , Ti( _OC2 Monohalogenated trialkoxytitanium such as H ₅ ) ₃ Cl, Ti(O _n -C ₄ H ₉ ) ₃ Cl, Ti(OC ₂ H ₅ ) ₃ Br; Ti(OCH ₃ ) ₄ , Ti(OC ₂ H ₅ ) ₄ and tetraalkoxytitanium such as Ti(O _n -C ₄ H ₉ ) ₄ . These titanium compounds may be used alone or in combination of two or more.
Among the above titanium compounds, preferred are halogen-containing titanium compounds, more preferred are titanium tetrahalides, and particularly preferred are titanium tetrachloride (TiCl ₄ ).

Magnesium compounds used in component (a) include magnesium compounds having a magnesium-carbon bond or a magnesium-hydrogen bond, such as dimethylmagnesium, diethylmagnesium, dipropylmagnesium, dibutylmagnesium, diamylmagnesium, dihexylmagnesium, didecylmagnesium, Examples include ethylmagnesium chloride, propylmagnesium chloride, butylmagnesium chloride, hexylmagnesium chloride, amylmagnesium chloride, butyl ethoxymagnesium, ethylbutylmagnesium, butylmagnesium hydride, and the like. These magnesium compounds can also be used in the form of a complex compound with, for example, organoaluminium, and may be in a liquid or solid state. Further suitable magnesium compounds include magnesium halides such as magnesium chloride, magnesium bromide, magnesium iodide, magnesium fluoride; magnesium methoxychloride, ethoxymagnesium chloride, isopropoxymagnesium chloride, butoxymagnesium chloride, octoxymagnesium chloride, alkoxymagnesium halides such as phenoxymagnesium chloride, methylphenoxymagnesium chloride; alkoxymagnesium halides such as ethoxymagnesium, isopropoxymagnesium, butoxymagnesium, n-octoxymagnesium, 2-ethylhexoxymagnesium; dimethoxymagnesium Examples include dialkoxymagnesium such as magnesium, diethoxymagnesium, dipropoxymagnesium, dibutoxymagnesium, and ethoxymethoxymagnesium; allyloxymagnesiums such as ethoxypropoxymagnesium, butoxyethoxymagnesium, phenoxymagnesium, and dimethylphenoxymagnesium. . These magnesium compounds may be used alone or in combination of two or more.

The electron donor compound used in component (a) preferably contains a phthalate compound as an essential component. When the catalyst (X) containing a phthalate compound as an electron donor is used, a polypropylene resin having surface impact resistance within the above range can be easily obtained.
Examples of phthalate compounds include monoethyl phthalate, dimethyl phthalate, methyl ethyl phthalate, monoisobutyl phthalate, mono-normal butyl phthalate, diethyl phthalate, ethyl isobutyl phthalate, ethyl normal butyl phthalate, di-n-propyl phthalate, diisopropyl phthalate, and di-n-propyl phthalate. Examples include n-butyl phthalate, diisobutyl phthalate, di-n-heptyl phthalate, di-2-ethylhexyl phthalate, di-n-octyl phthalate, dineopentyl phthalate, didecyl phthalate, benzyl butyl phthalate, and diphenyl phthalate. Among them, diisobutyl phthalate is particularly preferred.

Examples of electron donor compounds in the solid catalyst other than phthalate compounds include succinate compounds and diether compounds.

The succinate compound may be an ester of succinic acid, or an ester of a substituted succinic acid having a substituent such as an alkyl group at the 1st or 2nd position of succinic acid. Specific examples include diethyl succinate, dibutyl succinate, diethyl methyl succinate, diethyl diisopropyl succinate, and diallyl ethyl succinate.

Examples of diether compounds include 2-(2-ethylhexyl)-1,3-dimethoxypropane, 2-isopropyl-1,3-dimethoxypropane, 2-butyl-1,3-dimethoxypropane, 2-sec-butyl-1,3-dimethoxypropane, 2-cyclohexyl-1,3-dimethoxypropane, 2-phenyl-1,3-dimethoxypropane, 2-tert-butyl-1,3-dimethoxypropane, 2-cumyl-1,3-dimethoxypropane, 2-(2-phenylethyl)-1,3-dimethoxypropane, 2-(2-cyclohexylethyl)-1,3-dimethoxypropane, 2-(p-chlorophenyl)-1,3-dimethoxypropane, 2-(diphenylmethyl)-1,3-dimethoxypropane, 2-(1-naphthyl)-1,3-dimethoxypropane, 2-(p-fluorophenyl)-1,3-dimethoxypropane, 2-( 1-decahydronaphthyl)-1,3-dimethoxypropane, 2-(p-tert-butylphenyl)-1,3-dimethoxypropane, 2,2-dicyclohexyl-1,3-dimethoxypropane, 2,2-diethyl-1,3-dimethoxypropane, 2,2-dipropyl-1,3-dimethoxypropane, 2,2-dibutyl-1,3-dimethoxypropane, 2,2-diethyl-1,3-diethoxypropane, 2,2-dicyclohexyl propyl-1,3-dimethoxypropane, 2,2-dipropyl-1,3-diethoxypropane, 2,2-dibutyl-1,3-diethoxypropane, 2-methyl-2-ethyl-1,3-dimethoxypropane, 2-methyl-2-propyl-1,3-dimethoxypropane, 2-propyl-2-pentyl-1,3-diethoxypropane, 2-methyl-2-benzyl-1,3-dimethoxypropane, 2-methyl-2-phenyl -1,3-dimethoxypropane, 2-methyl-2-cyclohexyl-1,3-dimethoxypropane, 2-methyl-2-methylcyclohexyl-1,3-dimethoxypropane, 2,2-bis(p-chlorophenyl)-1,3-dimethoxypropane, 2,2-bis(2-phenylethyl)-1,3-dimethoxypropane, 2,2-bis(2-cyclohexylethyl)-1,3-dimethoxypropane, 2-methyl-2-iso butyl-1,3-dimethoxypropane, 2-methyl-2-(2-ethylhexyl)-1,3-dimethoxypropane, 2,2-bis(2-ethylhexyl)-1,3-dimethoxypropane, 2,2-bis(p-methylphenyl)-1,3-dimethoxypropane, 2-methyl-2-isopropyl-1,3-dimethoxypropane, 2,2-diisobutyl-1,3-dimethoxypropane, 2,2-diphenyl-1,3-dimethoxypropane 2,2-dibenzyl-1,3-dimethoxypropane, 2-isopropyl-2-cyclopentyl-1,3-dimethoxypropane, 2,2-bis(cyclohexylmethyl)-1,3-dimethoxypropane, 2,2-diisobutyl-1,3-diethoxypropane, 2,2-diisobutyl-1,3-dibutoxypropane, 2-isobutyl-2-isopropyl-1,3-dimethoxypropane, 2,2-di-sec 1,3-diethers such as 2-butyl-1,3-dimethoxypropane, 2,2-di-tert-butyl-1,3-dimethoxypropane, 2,2-dineopentyl-1,3-dimethoxypropane, 2-isopropyl-2-isopentyl-1,3-dimethoxypropane, 2-phenyl-2-benzyl-1,3-dimethoxypropane, and 2-cyclohexyl-2-cyclohexylmethyl-1,3-dimethoxypropane.
Further specific examples of the 1,3-diether compounds include the following: 1,1-bis(methoxymethyl)-cyclopentadiene;
1,1-bis(methoxymethyl)-2,3,4,5-tetramethylcyclopentadiene; 1,1-bis(methoxymethyl)-2,3,4,5-tetraphenylcyclopentadiene;
1,1-bis(methoxymethyl)-2,3,4,5-tetrafluorocyclopentadiene;
1,1-bis(methoxymethyl)-3,4-dicyclopentylcyclopentadiene;
1,1-bis(methoxymethyl)indene;
1,1-bis(methoxymethyl)-2,3-dimethylindene;
1,1-bis(methoxymethyl)-4,5,6,7-tetrahydroindene;
1,1-bis(methoxymethyl)-2,3,6,7-tetrafluoroindene;
1,1-bis(methoxymethyl)-4,7-dimethylindene;
1,1-bis(methoxymethyl)-3,6-dimethylindene;
1,1-bis(methoxymethyl)-4-phenylindene;
1,1-bis(methoxymethyl)-4-phenyl-2-methylindene;
1,1-bis(methoxymethyl)-4-cyclohexylindene;
1,1-bis(methoxymethyl)-7-(3,3,3-trifluoropropyl)indene;
1,1-bis(methoxymethyl)-7-trimethylsilyl indene;
1,1-bis(methoxymethyl)-7-trifluoromethylindene;
1,1-bis(methoxymethyl)-4,7-dimethyl-4,5,6,7-tetrahydroindene;
1,1-bis(methoxymethyl)-7-methylindene;
1,1-bis(methoxymethyl)-7-cyclopentylindene;
1,1-bis(methoxymethyl)-7-isopropylindene;
1,1-bis(methoxymethyl)-7-cyclohexylindene;
1,1-bis(methoxymethyl)-7-tert-butylindene;
1,1-bis(methoxymethyl)-7-tert-butyl-2-methylindene;
1,1-bis(methoxymethyl)-7-phenylindene;
1,1-bis(methoxymethyl)-2-phenylindene;
1,1-bis(methoxymethyl)-1H-benzindene;
1,1-bis(methoxymethyl)-1H-2-methylbenzindene;
9,9-bis(methoxymethyl)fluorene;
9,9-bis(methoxymethyl)-2,3,6,7-tetramethylfluorene;
9,9-bis(methoxymethyl)-2,3,4,5,6,7-hexafluorofluorene;
9,9-bis(methoxymethyl)-2,3-benzofluorene;
9,9-bis(methoxymethyl)-2,3,6,7-dibenzofluorene;
9,9-bis(methoxymethyl)-2,7-diisopropylfluorene;
9,9-bis(methoxymethyl)-1,8-dichlorofluorene;
9,9-bis(methoxymethyl)-2,7-dicyclopentylfluorene;
9,9-bis(methoxymethyl)-1,8-difluorofluorene;
9,9-bis(methoxymethyl)-1,2,3,4-tetrahydrofluorene;
9,9-bis(methoxymethyl)-1,2,3,4,5,6,7,8-octahydrofluorene;
9,9-bis(methoxymethyl)-4-tert-butylfluorene.

Examples of the halogen atom constituting component (a) include fluorine, chlorine, bromine, iodine, or a mixture thereof, with chlorine being particularly preferred.

Examples of the organoaluminum compound of component (a) include trialkylaluminums such as triethylaluminum and tributylaluminum, trialkenylaluminums such as triisoprenylaluminum, dialkylaluminum alkoxides such as diethylaluminum ethoxide and dibutylaluminum butoxide, alkylaluminum sesquialkoxides such as ethylaluminum sesquiethoxide and butylaluminum sesquibutoxide, R ¹ _2.5 Al(OR ² ) _0.5 (R ¹ , R ² are hydrocarbon groups which may be different or the same. ) having an average composition represented by the formula (I), dialkylaluminum halides such as diethylaluminum chloride, dibutylaluminum chloride, and diethylaluminum bromide, alkylaluminum sesquihalides such as ethylaluminum sesquichloride, butylaluminum sesquichloride, and ethylaluminum sesquibromide, alkylaluminum dihalides such as ethylaluminum dichloride, propylaluminum dichloride, and butylaluminum dibromide, partially halogenated alkylaluminums such as dialkylaluminum hydrides such as diethylaluminum hydride and dibutylaluminum hydride, alkylaluminum dihydrides such as ethylaluminum dihydride and propylaluminum dihydride, partially hydrogenated alkylaluminums such as ethylaluminum ethoxychloride, butylaluminum butoxychloride, and partially alkoxylated and halogenated alkylaluminums such as ethylaluminum ethoxybromide, butylaluminum butoxychloride, and ethylaluminum ethoxybromide, etc. may be mentioned. The above component (I) may be used alone or in combination of two or more kinds.

As the external electron donor compound of component (c), an organosilicon compound is used.
Preferred organosilicon compounds include, for example, trimethylmethoxysilane, trimethylethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diisopropyldimethoxysilane, t-butylmethyldimethoxysilane, t-butylmethyldiethoxysilane, t-amylmethyldiethoxy Silane, diphenyldimethoxysilane, phenylmethyldimethoxysilane, diphenyldiethoxysilane, bis o-tolyldimethoxysilane, bis m-tolyldimethoxysilane, bis p-tolyl dimethoxysilane, bis p-tolyl diethoxysilane, bisethylphenyl dimethoxysilane , dicyclopentyldimethoxysilane, dicyclohexyldimethoxysilane, cyclohexylmethyldimethoxysilane, cyclohexylmethyldiethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, methyltrimethoxysilane, n-propyltriethoxysilane, decyltrimethoxysilane Methoxysilane, decyltriethoxysilane, phenyltrimethoxysilane, γ-chloropropyltrimethoxysilane, methyltriethoxysilane, vinyltriethoxysilane, t-butyltriethoxysilane, thexyltrimethoxysilane, n-butyltriethoxysilane , iso-butyltriethoxysilane, phenyltriethoxysilane, γ-aminopropyltriethoxysilane, chlortriethoxysilane, ethyltriisopropoxysilane, vinyltributoxysilane, cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, 2-norbornane Trimethoxysilane, 2-norbornanetriethoxysilane, 2-norbornanemethyldimethoxysilane, ethyl silicate, butyl silicate, trimethylphenoxysilane, methyltriallyloxysilane, vinyltris (β-methoxyethoxysilane), vinyltriacetoxy Silane, dimethyltetraethoxydisiloxane, methyl(3,3,3-trifluoro-n-propyl)dimethoxysilane, cyclohexylethyldimethoxysilane, cyclopentyl-t-butoxydimethoxysilane, diisobutyldimethoxysilane, isobutylisopropyldimethoxysilane, n- Propyltrimethoxysilane, di-n-propyldimethoxysilane, t-butylethyldimethoxysilane, t-butylpropyldimethoxysilane, t-butyl-t-butoxydimethoxysilane, isobutyltrimethoxysilane, cyclohexylisobutyldimethoxysilane, di-sec -Butyldimethoxysilane, isobutylmethyldimethoxysilane, bis(decahydroisoquinolin-2-yl)dimethoxysilane, diethylaminotriethoxysilane, dicyclopentyl-bis(ethylamino)silane, tetraethoxysilane, tetramethoxysilane, isobutyltriethoxysilane , t-butyltrimethoxysilane, i-butyltrimethoxysilane, i-butylsec-butyldimethoxysilane, ethyl(perhydroisoquinolin-2-yl)dimethoxysilane, tri(isopropenyloxy)phenylsilane, i-butyl i-propyl Examples include dimethoxysilane, cyclohexyl i-butyldimethoxysilane, cyclopentyl i-butyldimethoxysilane, cyclopentylisopropyldimethoxysilane, phenyltriethoxylane, p-tolylmethyldimethoxysilane, and the like.
Among these, ethyltriethoxysilane, n-propyltriethoxysilane, n-propyltrimethoxysilane, t-butyltriethoxysilane, t-butylmethyldimethoxysilane, t-butylmethyldiethoxysilane, t-butylethyldimethoxy Silane, t-butylpropyldimethoxysilane, t-butylt-butoxydimethoxysilane, t-butyltrimethoxysilane, i-butyltrimethoxysilane, isobutylmethyldimethoxysilane, i-butylsec-butyldimethoxysilane, ethyl (perhydroisoquinoline) 2-yl)dimethoxysilane, bis(decahydroisoquinolin-2-yl)dimethoxysilane, tri(isopropenyloxy)phenylsilane, thexyltrimethoxysilane, vinyltriethoxysilane, phenyltriethoxysilane, phenyltrimethoxysilane, Vinyltributoxysilane, diphenyldimethoxysilane, diisopropyldimethoxysilane, diisobutyldimethoxysilane, i-butyl i-propyldimethoxysilane, cyclopentyl t-butoxydimethoxysilane, dicyclopentyldimethoxysilane, cyclohexylmethyldimethoxysilane, cyclohexyl i-butyldimethoxysilane, Cyclopentyl i-butyldimethoxysilane, cyclopentylisopropyldimethoxysilane, di-sec-butyldimethoxysilane, diethylaminotriethoxysilane, tetraethoxysilane, tetramethoxysilane, isobutyltriethoxysilane, phenylmethyldimethoxysilane, phenyltriethoxylane, bis p -Tolyldimethoxysilane, p-tolylmethyldimethoxysilane, dicyclohexyldimethoxysilane, cyclohexylethyldimethoxysilane, 2-norbornanetriethoxysilane, 2-norbornanemethyldimethoxysilane, diphenyldiethoxysilane, methyl (3,3,3-trifluoro -n-propyl) dimethoxysilane, ethyl silicate, and the like are preferred.
The above component (c) may be used alone or in combination of two or more.

Organosilicon compounds play an important role in adjusting the amount of xylene insolubles in propylene homopolymers, which is an index of stereoregularity.When other catalyst components are the same, the amount of xylene insolubles depends on the type and amount of organosilicon compounds and polymerization temperature, but even when an appropriate organosilicon compound is used, the amount of organosilicon compounds is significantly reduced when the amount of organosilicon compounds falls below a certain value, except for diether catalysts.Therefore, when the polymerization temperature is 75°C, the lower limit of the molar ratio of organosilicon compounds to organoaluminum compounds (organosilicon compounds/organoaluminum compounds) is preferably 0.015, more preferably 0.018.The upper limit of this ratio is preferably 0.30, more preferably 0.20, and even more preferably 0.10.
When using a phthalate-based compound as an internal electron donor compound, increasing the polymerization temperature increases the amount of xylene insoluble matter, so the lower and upper limits of the preferred molar ratio of the organosilicon compound to the organoaluminum compound (organosilicon compound/organoaluminum) are reduced.Specifically, when using a phthalate-based compound to polymerize at 80°C, the lower limit of the molar ratio is preferably 0.010, more preferably 0.015, and even more preferably 0.018.The upper limit of the molar ratio is preferably 0.20, more preferably 0.14, and even more preferably 0.08.

As the catalyst (X), it is preferable that component (A) is a trialkylaluminum such as triethylaluminum or triisobutylaluminum, and component (C) is an organosilicon compound such as dicyclopentyldimethoxysilane, cyclohexylmethyldimethoxysilane, or diisopropyldimethoxysilane.

The method for obtaining the polymerization mixture by the multistage polymerization method is not limited to the above method, and the propylene polymer (component (a1)) may be polymerized in a plurality of polymerization reactors, or the ethylene-α-olefin copolymer (component (a2)) may be polymerized in a plurality of polymerization reactors.
The polymerization mixture may be obtained by using a polymerization vessel having a gradient of monomer concentration or polymerization conditions. For example, such a polymerization vessel may have at least two polymerization zones joined together, and the monomers may be polymerized by gas phase polymerization.
Specifically, in the presence of a catalyst, a monomer is supplied to a polymerization zone consisting of an uprising pipe and polymerized, and a monomer is supplied to a downcomer pipe connected to the uprising pipe and polymerized, and a polymerization product is recovered while circulating between the uprising pipe and the downcomer pipe. In this method, a means is provided for completely or partially preventing the gas mixture present in the uprising pipe from entering the downcomer pipe. Also, a gas and/or liquid mixture having a composition different from that of the gas mixture present in the uprising pipe is introduced into the downcomer pipe. For example, the method described in JP-A-2002-520426 can be applied to this polymerization method.

(Method for producing ethylene/α-olefin copolymer (B))
The ethylene/α-olefin copolymer (B) can be produced by a known method using a metallocene catalyst or a half-metallocene catalyst during polymerization (for example, the method described in International Publication WO2006/102155).
During the polymerization, a known molecular weight regulator such as a chain transfer agent (for example, hydrogen or diethyl zinc) may be used.

Examples and comparative examples are shown below, but the present invention is not limited to the following examples.

<Preparation of catalyst (X)>
A solid catalyst with TiCl ₄ and diisobutyl phthalate as an internal donor supported on MgCl ₂ was prepared by the method described in Example 5, lines 46-53 of EP 728,769. Specifically, it was performed as follows.

The microspheroidal MgCl ₂ ·2.1C ₂ H ₅ OH was prepared as follows: In a 2 L autoclave equipped with a turbine agitator and an aspiration pipe, 48 g of anhydrous MgCl ₂ , 77 g of anhydrous C ₂ H ₅ OH, and 830 mL of kerosene were placed under inert gas at room temperature. The contents were heated to 120°C with stirring to produce an adduct between MgCl ₂ and the alcohol, which was melted and mixed with the dispersant. The nitrogen pressure in the autoclave was maintained at 15 atm. The aspiration pipe of the autoclave was heated to 120°C from the outside using a heating jacket. The aspiration pipe had an inner diameter of 1 mm and a length of 3 m from one end of the heating jacket to the other. The mixture was made to flow through this pipe at a speed of 7 m/sec. At the outlet of the pipe, the dispersion was collected under stirring in a 5 L flask containing 2.5 L of kerosene and cooled externally by a jacket whose initial temperature was maintained at -40°C. The final temperature of the dispersion was 0°C. The spherical solid product, constituting the dispersed phase of the emulsion, _was allowed to settle, separated by filtration, washed with heptane and _dried . All these operations were carried out in an inert gas atmosphere. _{MgCl2.3C2H5OH} was obtained in the form of solid spherical particles with a maximum diameter of less than 50 μm. The yield was 130 g. The alcohol was removed from the product thus obtained by gradually increasing the temperature from 50°C to 100°C in a nitrogen stream until the alcohol content per mole of _MgCl2 was reduced to 2.1 moles.

A 500 mL cylindrical glass reactor equipped with a filtration barrier was charged at 0° C. with 225 mL of TiCl ₄ and 10.1 g (54 mmol) of microspheroidal MgCl ₂ .2.1C ₂ H ₅ OH obtained as described above. was added over a period of 15 minutes while stirring the contents. Thereafter, the temperature was raised to 40° C. and 9 mmol of diisobutyl phthalate was added. The temperature was increased to 100° C. over 1 hour and stirring continued for an additional 2 hours. TiCl ₄ was then removed by filtration and 200 mL of TiCl ₄ was added with stirring at 120° C. for an additional hour. Finally, the contents were filtered and washed with n-heptane at 60° C. until the filtrate was completely free of chloride ions. The catalyst component thus obtained contained 3.3% by mass of Ti and 8.2% by mass of diisobutyl phthalate.

The above solid catalyst was contacted with triethylaluminum (TEAL) as an organoaluminum compound and dicyclopentyldimethoxysilane (DCPMS) as an external electron donor compound in amounts such that the mass ratio of TEAL to the solid catalyst was 20 and the mass ratio of TEAL/DCPMS was 10 (equivalent to the molar ratio of organosilicon compound/organoaluminum described above of 0.05) for 24 minutes at 12°C to obtain catalyst (X).

<Preparation of copolymer 1>
Prepolymerization was carried out by holding the obtained catalyst (X) in a suspended state at 20° C. for 5 minutes in liquid propylene.
The obtained prepolymerized product was introduced into the first stage polymerization reactor of a polymerization apparatus equipped with two stages of polymerization reactors in series, and propylene was supplied to produce a propylene homopolymer. Subsequently, propylene homopolymer, propylene, and ethylene were supplied to the second stage polymerization reactor to produce an ethylene-propylene copolymer. During the polymerization, temperature and pressure were adjusted and hydrogen was used as a molecular weight regulator.
The polymerization temperature and the ratio of reactants are as follows: In the first reactor, the polymerization temperature and hydrogen concentration are 70°C and 1.20 mol%, respectively, and in the second reactor, the polymerization temperature, hydrogen concentration, and ethylene and propylene The proportions of ethylene relative to the total were 80° C., 2.96 mol%, and 0.26 mol ratio, respectively. Further, the ratio of the first and second stage polymerization times was adjusted so that the amount of ethylene-propylene copolymer was 33% by mass. By the above method, the desired copolymer 1 was obtained.
The obtained copolymer 1 is a polymerized mixture of component (a1), which is a propylene polymer constituting the continuous phase, and component (a2), which is an ethylene-propylene copolymer constituting the rubber phase, and is It is a polypropylene resin (A).

Regarding copolymer 1, MFR of component (a1), intrinsic viscosity of component (a1), mass ratio component (a2)/[component (a1) + component (a2)], ethylene-derived unit content in component (a2) amount, XSIV of component (a1) + component (a2), ratio expressed as {[XSIV of component (a1) + component (a2)]/[intrinsic viscosity of component (a1)]}, component (a1) + The MFR of component (a2) was as shown in Table 1.

<Production of Copolymers 2 to 8>
Copolymers 2 to 8 consisting of a polymerization mixture of components (a1) and (a2) were produced by the same production method as for copolymer 1, except that the ratio of the polymerization times in the first stage and the second stage and the proportion of ethylene to the total of ethylene and propylene in the second stage reactor were changed so that the mass ratio of component (a2)/[component (a1) + component (a2)] and the content of ethylene-derived units in component (a2) were the proportions shown in Table 1, and the hydrogen concentrations in the first stage and second stage were changed to adjust the MFR and XSIV of component (a1) + component (a2).
These copolymers were measured in the same manner as for copolymer 1. The measured values are shown in Table 1.

<Production of Copolymers R1 to R4>
Copolymers R1 to R4 consisting of a polymerization mixture of components (a1) and (a2) were obtained by the same production method as for copolymer 1, except that the ratio of the polymerization times in the first stage and the second stage and the proportion of ethylene to the total of ethylene and propylene in the second stage reactor were changed so that the mass ratio of component (a2)/[component (a1) + component (a2)] and the content of ethylene-derived units in component (a2) were the proportions shown in Table 1, and the hydrogen concentrations in the first stage and the second stage were changed to adjust the MFR and XSIV of component (a1) + component (a2).
These copolymers were measured in the same manner as for copolymer 1. The measured values are shown in Table 1.

The measurement results in Table 1 are values measured by the following measurement method.

<Total ethylene amount of copolymer, ethylene-derived unit content of component (a1)>
A copolymer sample dissolved in a mixed solvent of 1,2,4-trichlorobenzene/deuterated benzene was measured using Bruker's AVANCE III HD400 ( ^13C resonance frequency 100 MHz) at a measurement temperature of 120°C and a flip angle of 45 degrees. ^{A 13} C-NMR spectrum was obtained under the conditions of a pulse interval of 7 seconds, a sample rotation rate of 20 Hz, and an integration count of 5000 times.
Using the spectrum obtained above, the total ethylene of the copolymer sample was determined by the method described in the literature by Kakugo, Y.Naito, K.Mizunuma and T.Miyatake, Macromolecules, 15, 1150-1152 (1982). The amount (mass%) was determined.
In addition, when measuring component (a1) as a sample, the total ethylene amount (mass %) obtained by the above method becomes the ethylene-derived unit content (mass %) of component (a1).

<Content of ethylene-derived units in component (a2)>
The ethylene-derived unit content (mass%) of component (a2) was calculated in the same manner as for the total ethylene amount, except that the integrated intensity T'ββ calculated by the following formula was used instead of the integrated intensity Tββ calculated when measuring the total ethylene amount of the copolymer by the method described in the above document.
T'ββ=0.98×Sαγ×A/(1−0.98×A)
Here, A=Sαγ/(Sαγ+Sαδ) and is calculated from Sαγ and Sαδ described in the above-mentioned document.
In a copolymer composed of components (a1) and (a2), when component (a1) contains ethylene units, the content of ethylene-derived units in component (a2) was calculated by the following formula when the mass ratio, component (a2)/[component (a1)+component (a2)], was clear from the polymerization conditions.
Ethylene-derived unit content of component (a2) (unit: mass%)=
[Total ethylene content of copolymer−Ethylene-derived unit content of component (a1)×Content of component (a1) in copolymer]
/ (content of component (a2) in the copolymer)

<Mass ratio component (a2)/[component (a1)+component (a2)]>
It was calculated using the following formula.
component (a2)/[component (a1)+component (a2)] (unit: mass %)=total ethylene amount in copolymer/(content of ethylene-derived units in component (a2)/100)

<Intrinsic Viscosity of Component (a1)>
The component (a1) separated from the first reactor was used as a sample, and the intrinsic viscosity was measured in tetralin at 135° C. using an automatic capillary viscosity measuring device (SS-780-H1, manufactured by Shibayama Scientific Instruments Manufacturing Co., Ltd.).

<MFR of component (a1)>
The component (a1) separated from the first-stage reactor was used as a sample. 0.05 g of H-BHT manufactured by Honshu Chemical Industry Co., Ltd. was added to 5 g of the sample, and the mixture was homogenized using a dry bland. The MFR was then measured at a temperature of 230° C. and a load of 2.16 kg in accordance with JIS K6921-2.

<XSIV of Polypropylene Resin (A) (Component (a1) + Component (a2))>
The xylene soluble portion of the polypropylene resin (A) was obtained by the following method, and the intrinsic viscosity (XSIV) of the xylene soluble portion was measured.
2.5 g of a sample of polypropylene resin (A) was placed in a flask containing 250 mL of o-xylene (solvent), and the mixture was stirred for 30 minutes using a hot plate and a reflux device while purging with nitrogen at 135° C. until completely dissolved, and then cooled at 25° C. for 1 hour. The solution thus obtained was filtered using filter paper. 100 mL of the filtrate after filtration was collected and transferred to an aluminum cup or the like, and evaporated to dryness at 140° C. while purging with nitrogen, and then allowed to stand at room temperature for 30 minutes to obtain a xylene-soluble portion.
The intrinsic viscosity was measured in tetrahydronaphthalene at 135° C. using an automatic capillary viscosity measuring device (SS-780-H1, manufactured by Shibayama Scientific Instruments Co., Ltd.).

[Examples 1 to 8, Comparative Examples 1 to 4]
Using the copolymer shown in Table 1, 0.2 parts by mass of B225 manufactured by BASF as an antioxidant and 0.0 parts of calcium stearate manufactured by Tannan Kagaku Kogyo Co., Ltd. as a neutralizing agent for 100 parts by mass of the copolymer. 0.05 parts by mass and 0.07 parts by mass of ADEKA STAB NA-11 as a nucleating agent were added, and the mixture was stirred and mixed for 1 minute using a Henschel mixer. The mixture was melt-kneaded and extruded at a cylinder temperature of 200° C. using a co-directional twin-screw extruder TEX-30α manufactured by JSW Corporation. After cooling the strand in water, it was cut with a pelletizer to obtain pellets of the polypropylene resin composition. Various physical properties of the polypropylene resin compositions obtained here and test pieces obtained from injection molded articles obtained using these were evaluated. The results are shown in Table 1.

The various physical properties in Table 1 were measured and evaluated using the following methods.

<Liquidity MFR>
The MFR of the polypropylene resin composition was measured under conditions of a temperature of 230° C. and a load of 2.16 kg based on JIS K6921-2.

<Rigidity and bending modulus>
According to JIS K6921-2, a polypropylene resin composition was injection molded into a multipurpose test piece (Type A1) as specified in JIS K7139 using an injection molding machine (FANUC ROBOSHOT S2000i manufactured by FANUC LTD.) under the conditions of a molten resin temperature of 200°C, a mold temperature of 40°C, an average injection speed of 200 mm/sec, a pressure holding time of 40 seconds, and a total cycle time of 60 seconds. The nozzle of the injection molding machine was a mixing nozzle (TMN16-07HPXW manufactured by Toray Engineering D Solutions Co., Ltd.) that is widely used industrially for the purpose of improving dispersibility. The obtained injection molded body was processed to a width of 10 mm, a thickness of 4 mm, and a length of 80 mm to obtain a test piece (Type B2) for measurement. The flexural modulus was measured using a precision universal testing machine (Autograph AG-X 10 kN) manufactured by Shimadzu Corporation under conditions of a temperature of 23° C., a relative humidity of 50%, a support distance of 64 mm, and a test speed of 2 mm/min.

<Crack type judgment: surface impact resistance>
A mold having a cavity of 70 mm x 70 mm x 3 mm thickness and a film gate was attached to an injection molding machine (FANUC ROBOSHOT S2000i manufactured by FANUC CORPORATION) equipped with a mixing nozzle. The mold temperature was set to 40°C, and pellets of the polypropylene resin composition were injected into the cavity to mold a test piece for measurement. Using a puncture impact tester (Hydroshot HITS-P10 manufactured by Shimadzu Corporation), a surface impact test of the test piece for measurement was carried out at -20°C in accordance with JIS K7211-2 as follows. In a tank adjusted to -20°C, the test piece for measurement was placed on a support table with a hole with an inner diameter of 40 mmφ, and fixed using a sample presser with an inner diameter of 40±2 mmφ. The test piece was struck at an impact speed of 4.4±0.2 m/s with a striker with a diameter of 20.0±0.2 mmφ having a hemispherical striking surface, and the fracture behavior was determined.

Using the test pieces after the surface impact test, the type of impact fracture behavior was determined in four stages: YD/YS/YU/NY according to JIS K7211-2.
The higher the evaluation stage, the better the surface impact resistance.
4: YD (Yielding caused by deep drawing)
3: YS (Yielding caused by stable cracking (at least partially))
2: YU (Yielding caused by unstable cracks)
1: NY (Fracture without yielding caused by unstable cracks)

<Charpy impact test (23°C); impact resistance>
A type A1 test piece obtained by the same procedure as the test piece used in the flexural modulus measurement in accordance with JIS K6921-2 was used, and processed to a width of 10 mm, a thickness of 4 mm, and a length of 80 mm using a notching tool A-4 manufactured by Toyo Seiki Seisaku-sho, Ltd. in accordance with JIS K7111-1, and then a 2 mm notch was made in the width direction to obtain a test piece for measurement of shape A. The obtained test piece for measurement was tested using a digital impact tester (DG-UB type) manufactured by Toyo Seiki Seisaku-sho, Ltd., under conditions of edgewise impact and 1 eA method at 23°C.
The higher the measured Charpy impact value, the better the impact resistance. Note that the unit of the measured values in the table is "kJ/m ² ", but for the sake of ease of reading the text in the table, we have used "kJ/m2". The same applies to the case of -20°C below.

<Charpy impact test (-20°C); Impact resistance>
Tests were conducted using the method described above at -20°C.
The higher the measured Charpy impact value, the better the impact resistance.

<Shrinkage rate>
The difference between the actual dimensions of a flat plate injection molded under constant molding conditions and filling rate in a mold with a thickness of 3 mm, width of 140 mm, and length of 300 mm attached to a Toshiba Machine Co., Ltd. EC160N II injection molding machine was measured in the length direction (MD) and width direction (TD), and the ratio to each actual dimension was expressed in thousandths and listed in the table. The average value (Av) of MD and TD was taken as the shrinkage rate of the composition. The lower the measured shrinkage rate, the smaller the linear expansion coefficient and the better the dimensional stability.

≪Effect≫
The molded products of Examples 1 to 8 are excellent in rigidity, impact resistance, and surface impact strength because they use polypropylene resin compositions having predetermined physical properties. In addition, the shrinkage rate after molding is small and the dimensional stability is excellent. If the Charpy value at 23°C is 40 kJ/m2 ^or higher, ductile fracture will occur at room temperature; if the cracking rating in the surface impact test at -20°C is 2 or higher, fracture due to plastic deformation will proceed even at low temperatures; A cracking rating of 3 or higher in the surface impact test at -20°C means that the plastic deformation progresses more stably. The progression of ductile fracture and plastic deformation means that sharp fracture surfaces and fragments are less likely to occur, making it particularly suitable for materials used in areas that are subject to impact, such as car doors, and large parts that are close to passengers. suitable. In the polypropylene resin composition according to the present invention, these can be achieved without the need for an expensive additional elastomer (component (B), which is an optional component).
In Comparative Examples 1, 2, and 4, the XSIV of component (a2) is high, so the cracking determination is poor. This means that the surface impact strength is poor as a physical property. Judgment 1 indicates that the material is unsuitable as an automobile interior material because there is a concern that sharp fractured surfaces or fragments may injure passengers when an impact is applied, such as during an accident.
Comparative Example 3 has a high content of ethylene-derived units in component (a2), and has poor impact resistance at room temperature (Charpy impact test).

Claims (6)

A polypropylene-based resin composition comprising a polypropylene-based resin (A) including a continuous phase made of a propylene polymer (a1) and a rubber phase made of a copolymer (a2) of ethylene and an α-olefin having 3 to 10 carbon atoms,
The content of the polypropylene-based resin (A) is 90% by mass or more and 100% by mass or less based on the total mass of the polypropylene-based resin composition,
The content of the propylene polymer (a1) is 64 to 70% by mass based on the total mass of the polypropylene-based resin (A),
The content of the copolymer (a2) is 30 to 36% by mass based on the total mass of the polypropylene-based resin (A),
The content of ethylene-derived units in the copolymer (a2) is 20 to 40% by mass based on the total mass of the copolymer (a2),
The polypropylene resin (A) has an intrinsic viscosity of 0.7 to 2.1 dL/g in tetrahydronaphthalene at 135° C.;
The polypropylene resin composition has an MFR of 20 to 36 g/10 min at a temperature of 230° C. and a load of 2.16 kg. The polypropylene resin composition according to claim 1, wherein the propylene polymer (a1) has an MFR of 30 to 150 g/10 minutes at a temperature of 230° C. and a load of 2.16 kg. The polypropylene resin composition according to claim 1, wherein the propylene polymer (a1) has an intrinsic viscosity of 0.89 to 1.26 dL/g in tetralin at 135°C. Expressed as {[Intrinsic viscosity of the xylene soluble portion of the polypropylene resin (A) in tetrahydronaphthalene at 135°C]/[Intrinsic viscosity of the propylene polymer (a1) in tetralin at 135°C]} The polypropylene resin composition according to claim 1, wherein the ratio of 0.4 to 2.3. The polypropylene-based resin composition according to any one of claims 1 to 4, wherein the propylene polymer (a1) and the copolymer (a2) are mixed by polymerization, and the polypropylene-based resin (A) is a polymerization mixture produced using a catalyst containing the following components (a) to (c):
(a) A solid catalyst containing magnesium, titanium, a halogen, and a phthalate-based compound as an electron donor compound. (b) An organoaluminum compound. (c) An organosilicon compound as an external electron donor compound. 6. The method for producing a polypropylene resin composition according to claim 5, wherein ethylene monomer is A method for producing a polypropylene resin composition, comprising the step of polymerizing an α-olefin monomer having 3 to 10 carbon atoms to obtain the polypropylene resin (A).
(a) Solid catalyst containing magnesium, titanium, halogen, and a phthalate compound as an electron donor compound as essential components (b) Organoaluminum compound (c) Organosilicon compound as an external electron donor compound